A recombinant protein expression system that improves yield and immunogenicity has been disclosed in U.S. Ser. No. 12/149,606, filed 5 May 2008, now U.S. Pat. No. 7,524,648 and U.S. Ser. No. 12/406,789, now U.S. Pat. No. 7,759,461; the contents of which are incorporated herein by reference. Said expression system includes the protein transduction domain (PTD) and Hsp40-J domain, and may improve yield and immunogenicity of the recombinant protein to be expressed.
U.S. Pat. No. 8,410,045 discloses that conjugating camptothecin with a cell penetrating peptide (CPP) may increase solubility, modify the pharmacokinetics, metabolism and tissue distribution properties of camptothecin.
US 20130137644 A1 discloses that conjugating a nucleic acid with a CPP may improve delivery efficacy of said nucleic acid into cells.
There is still a need to develop a system or method that further enhances the cell transduction efficiency of an active agent.